You don't have to fix it because it's intended like that. The password is stored in isp_isp_user only for a short moment after you've created the user; after it has been written to /etc/shadow it is removed from isp_isp_user for security reasons (imagine someone hacks your MySQL database and finds all those passwords...).
The status field is only for internal use.

Thanks falko,
I'm trying to setup postfix to use ispconfig db instead of a custom mysql database. I'm thinking that this is possible because all needed information are already stored on ispconfig db. I think a litle hack in ispconfig_isp_user.lib.php may help me. I don't know exactly and script comments in German don't help me.
I can use some help here.

First you will have to add a new password field. You cannot use the current field for postfix authentication because ISPConfig needs to prepend some chracters to the password to recognize if its encrypted.

Then you will have to add some code in the file /home/admispconfig/ispconfig/lib/ispconfig_isp_user.lib.php